The present invention relates in general to semiconductor packaging and, more particularly, to wire bonding between contacts that are positioned at substantially the same height or level in a semiconductor package.
An aspect of semiconductor packaging involves a wire bonding process. A conventional wire bonding process may use a conductive wire to connect a semiconductor die to a lead of a lead frame. This allows the semiconductor die to electrically communicate with external systems. The wire bonding process typically produces a loop in the conductive wire. A height of the loop determines a minimum allowable thickness of a semiconductor package.
Semiconductor packages are continually being designed to be more compact. This can be accomplished by using multi die packages, reducing thickness of the packages, and/or minimizing size of the packages. Loop height impacts each of these options.
Conventional methods of reducing loop height between contacts at different levels may include pulling the bonding wire downward. This increases stress in the bonding wire, however, and can lead to fracturing or cracking near ball bonds. Other methods include forming a folded loop in the bonding wire or forming a depression on a neck portion of the bonding wire. Quality of these methods is difficult to assess, however, and they generally reduce wire strength. One method that has been used with some success includes forming a first ball bond on a higher contact, then attaching a bonding wire to a lower contact using a ball bond, and then attaching the bonding wire to the higher contact using a stitch bond.
For contacts at the same height or level, the loop height is typically reduced by pulling the bonding wire downward. As explained above, this increases stress in the bonding wire and can lead to fracturing or cracking near ball bonds. The stress can be reduced by separating the contacts farther apart and lengthening the bonding wire. However, this increases lateral dimensions and size of the package. Other methods that have been used to reduce loop height when connecting contacts at different levels fail to provide the same benefit when used with contacts positioned at the same height or level.
Thus, there is a need to reduce loop height in bonding wires used to connect contacts that are positioned at the same height or level without increasing wire length.